How do I correct the IMAP command "UID COPY" (to trash) error after upgrading to High Sierra v 10.13?

Well mine is working fine after restarting Mail. Might be Yahoo servers are having issues. I also had a problem with my iPhone and the same Yahoo account. I had to re add my password there. So, it may be a password issue. Try disabling the account, then re enable it. Or, delete the account and add it back.

Have you tried quitting Mail to restart it? That happened to me this morning and it corrected the communication error.

That appears to be a communication problem between the Mail app and Yahoo! Mail.

A possible workaround is to wait a few minutes between deleting messages. You can delete more than one at a time: make a continuous selection using a Shift key, or a discontinuous selection using ⌘.

We'll have to wait for Yahoo! to fix it, or Apple, or for both of them as they point fingers at each other.

Yahoo acknowledged the problem earlier today and is promising a fix by the end of next week.

Describe that error in greater detail: where you see it, how and when it appears... etc. Explain it as though I cannot see what you're doing with your Mac.